STATISTICS statement to associate a statistics type (or default statistics) containing functions relevant to statistics collection, selectivity, or cost with one or more columns, standalone functions, packages, types, domain indexes, or indextypes.
For a listing of all current statistics type associations, query the
USER_ASSOCIATIONS data dictionary view. If you analyze the object with which you are associating statistics, then you can also query the associations in the
ANALYZE for information on the order of precedence with which
ANALYZE uses associations
To issue this statement, you must have the appropriate privileges to alter the base object (table, function, package, type, domain index, or indextype). In addition, unless you are associating only default statistics, you must have execute privilege on the statistics type. The statistics type must already have been defined.
CREATE TYPE for information on defining types
Specify one or more table columns. If you do not specify
schema, then Oracle Database assumes the table is in your own schema.
Specify one or more standalone functions, packages, user-defined data types, domain indexes, or indextypes. If you do not specify
schema, then Oracle Database assumes the object is in your own schema.
FUNCTIONSrefers only to standalone functions, not to method types or to built-in functions.
TYPESrefers only to user-defined types, not to built-in SQL data types.
Restriction on function_association
You cannot specify an object for which you have already defined an association. You must first disassociate the statistics from this object.
Specify the statistics type (or a synonym for the type) being associated with column, function, package, type, domain index, or indextype. The
statistics_type must already have been created.
NULL keyword is valid only when you are associating statistics with a column or an index. When you associate a statistics type with an object type, columns of that object type inherit the statistics type. Likewise, when you associate a statistics type with an indextype, index instances of the indextype inherit the statistics type.You can override this inheritance by associating a different statistics type for the column or index. Alternatively, if you do not want to associate any statistics type for the column or index, then you can specify
NULL in the
Restriction on Specifying Statistics Type
You cannot specify
NULL for functions, packages, types, or indextypes.
Oracle Database Data Cartridge Developer's Guide for information on creating statistics collection functions
Specify default costs for standalone functions, packages, types, domain indexes, or indextypes. If you specify this clause, then you must include one number each for CPU cost, I/O cost, and network cost, in that order. Each cost is for a single execution of the function or method or for a single domain index access. Accepted values are integers of zero or greater.
Specify as a percent the default selectivity for predicates with standalone functions, types, packages, or user-defined operators. The
default_selectivity_clause must be a number between 0 and 100. Values outside this range are ignored.
Restriction on the default_selectivity_clause
You cannot specify
SELECTIVITY for domain indexes or indextypes.
This clause is relevant only for statistics on
TABLESto indicate that the storage of statistics data is to be managed by the system. The type you specify in
statistics_typeshould be storing the statistics related information in tables that are maintained by the system. Also, the indextype you specify must already have been created or altered to support the
TABLESto indicate that the tables that store the user-defined statistics will be managed by the user. This is the default behavior.
Associating Statistics: Example
This statement creates an association for the standalone package
emp_mgmt. See Oracle Database PL/SQL Language Reference for the example that creates this package.
ASSOCIATE STATISTICS WITH PACKAGES emp_mgmt DEFAULT SELECTIVITY 10;
Specifying Default Cost: Example
This statement specifies that using the domain index
salary_index, created in "Using Extensible Indexing", to implement a given predicate always has a CPU cost of 100, I/O cost of 5, and network cost of 0.
ASSOCIATE STATISTICS WITH INDEXES salary_index DEFAULT COST (100,5,0);
The optimizer will use these default costs instead of calling a cost function.